Hemostasis valves (also sometimes referred to as "Y-connectors" and "Touhy-Borst valves") are commonly used in certain medical procedures. A guide catheter is connected to the distal end of the valve, and an operating instrument, such as a guide wire or balloon catheter, is inserted into the proximal end and through the guide catheter to the desired location in the patient. After the operating instrument is in place, the valve is closed to keep blood from leaking out of the patient ("hemostasis").
One of the problems with current hemostasis valves is that they are cumbersome to operate, taking a long time to open and close. Most employ a Touhy-Borst sealing mechanism such as that described in U.S. Pat. No. 4,886,507. A threaded cap deforms an O-ring into a tapered opening until the O-ring clamps down on the operating instrument. Each time the operating instrument is adjusted, the cap must be unthreaded before and then rethreaded after the manipulation. During the time that the valve is open, blood leaks from the patient and/or contrast media is lost. Inaccurate blood pressure readings also occur. There is also a risk of air emboli when the valve is open, particularly when removing the operating instrument.
Another problem with prior art hemostasis valves, such as Touhy-Borst valves, is that significant mechanical force must be applied to the operating instrument in order to maintain the seal. This is particularly a problem at higher system pressures, and when pressure spikes occur, such as when flushing the system with saline or introducing contrast media. The often delicate drive shaft of the operating instrument can be crushed by the force of the seal. The high force seal also prevents moving the operating instrument while the valve is closed.
One attempt at addressing some of these problems is shown in the '507 patent. In addition to a Touhy-Borst, this design includes a membrane having a fixed circular opening for sealing shafts within a certain diameter range. This sealing arrangement, however, still relies solely on a mechanical sealing system which requires high shaft forces at high system pressures. It also incorporates the same threaded Touhy-Borst valve, which requires the cap to be manually threaded in order to close the valve. The fixed opening membrane would also be helpful only with operating instruments in a particular diameter range.
Hemostasis systems typically have a perfusion port used to flush the system with saline in order to prevent blood clots from being formed. This is done by a technician periodically during the procedure, which takes time and may interrupt the procedure. The blood pressure readings are also inaccurate during the flush.
What has been needed is a hemostasis valve which opens and closes easier, maintains a seal at higher pressures without damaging the instrument, and permits movement of the instrument while maintaining a seal. What has also been needed is a hemostasis system which reduces or eliminates the need for periodic flushing. What has also been needed is a hemostasis assembly which reduces blood loss and the risk of air emboli while the valve is open.